In general, the development of a turret considers several specific parameters, which, in most cases and to the extent possible, lead to the development of a single structure resulting from the optimization of each of these parameters.
The aforementioned parameters pertain to:                the mass of the turret,        the ballistic protection,        the caliber of the primary weapon, namely the cannon,        the quantity and type of ammunition to be stored, and the means for loading the latter (manual or automatic),        the dimensions of the vehicle on which the turret is associated,        the transport means of the vehicle/turret assembly,        the contractual constraints imposed by the user,        etc.        
Thus, the turrets typically designed are non-interchangeable or even non-modular, which means that it is necessary to redefine a complete structure for each new user and/or each new mission.
In other words, upstream, the base element, the shell, or even its architecture are subject to the same parameters, i.e., it is only usable under very specific conditions. That is why the modularity of the turret is often reduced to its simplest expression in light of the unique nature of each developed project. For each new project, it is necessary to re-think the architectural design based on the user's needs, which means that in turn, the shell is not interchangeable with respect to certain inner and/or outer modules.
Currently, the proposed solutions are based on the fact that the shell of the turret is defined based on the specificities requested by the user, without taking into account the interchangeability of certain structures to be grafted. In other words, in most configurations, the modularity aspect is not present, given that the design of said shell is associated with a single project.
The following documents have been identified in the state of the art.
In document US 20040183322, a tank provided with a passenger compartment supported by traction means using tracks and an armed station positioned on the roof of the passenger compartment such that inside the latter is divided into three regions: i) “front”, in which the traction mechanisms and the driver's seat are located, ii) “rear”, where the crew seats appear, and iii) “intermediate”, suitable for different purposes depending on the design of the vehicle, in particular for the adaptation of the turret and/or at least one seat for the operators of the armed station and/or a storage compartment for ammunition and loading devices. The first two regions have the same function for all alternatives of the vehicle, while the third region is freer.
Document WO2009004136 discloses a light military vehicle combining a chassis equipped with mobility means and at least one armored passenger cabin fastened to the chassis such that it can be disassembled by securing means.
Document WO2004017012 discloses a rolling armored vehicle formed by several compartments: i) a traction section, and ii) a mission section able to be detached from the rear part of the traction section and able to be coupled thereto via a vertical separation plane.
Document WO2013127654 discloses a turret for an armored vehicle including an invariable and rigid metal structural unit having a central position in the turret, on the one hand, and at least one interchangeable module able to be disassembled by securing means, on the other hand.
Document FR 2,579,946 discloses a versatile motor vehicle with tracks comprising a shell with tracks. On the horizontal top of the chassis of the shell, a plane is applied, on the upper face of which an element is mounted completing the architecture of the vehicle, quick assembly means being provided both for mounting the interface on the chassis of the shell and for mounting the element completing the architecture of the vehicle.
Document DE19720815 discloses a combat structure having various divided zones, one of which relates to the combat zone able to accommodate crewmembers as well as a set of electronic elements and a cooling system.
Document FR 3,017,700 discloses a modular weapon station comprising a rotating frame suitable for being mounted on a platform, and including a removable cradle with a weapon mounted thereon.
Document DE3836718 discloses a turret characterized by a specific journal system making it possible to interchange a 105 mm caliber cannon and a 120 mm caliber cannon simply by modifying the height of the journal axis for armored vehicles of different sizes.
Document WO 2015/004569 A1 discloses a turret comprising a hollow casing provided with a gun, such as a cannon, said casing comprising: a front portion or shell, on which there is mounted said gun and which defines a front cavity, which at least partially houses said gun; and a rear portion or tail, which defines a rear cavity, which houses at least one between a projectile magazine and a mechanism to load the projectiles into the breech of said gun; said front portion or shell and said rear portion or tail being distinct from one another and being mutually mechanically assembled so that said cavities at least partially communicate with one another.
Other documents, such as EP 2,151,659, EP 1,318,374, EP 2,195,601, EP 1,955,003, EP 1,508,765, EP 1,468,240, U.S. Pat. No. 9,194,664, WO 2013/010110, U.S. Pat. Nos. 7,513,187, 4,601,230, 3,566,742 and WO 2016/060719, are of some interest, but are less significant than the documents described above.
This approach can be likened to an automobile assembly line, where the shell is associated with the chassis, and the set of inner and/or outer modules is defined as being the component elements of the final vehicle corresponding to the user's wishes and the functional, operational, ecological, etc. market requirements/standards.